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Dormancy

    The research conducted within this theme aims to gain insight into the progression of dormancy under mild winter conditions and the impact of insufficient winter chill on fruit production. Dormancy release is also studied to potentially identify new and safer rest-breaking chemicals. Furthermore, it is becoming increasingly evident that the induction of dormancy under mild, local conditions requires further study. To this end, we are utilising the Pro-Hort ecophysiology platform. It consists of 10 genotypes each of apple, plum, pear and cherry varying in chill (and heat) requirements planted at three climatically contrasting sites. The platform allows the researchers to tease apart the effect of chill and heat requirements on the adaptability of cultivars to local conditions. Additionally, it will enable us to correlate the output of the various chill models with vegetative bud break and flowering data to identify the most suitable model for South African conditions.

    In terms of completed projects, Dr Esmé Louw set out to quantify the impact of insufficient winter chill on apple fruit quality. She found considerable variation in fruit maturity of Golden Delicious apples between trees within an orchard and between different positions on the tree. However, the extent of variation was similar in the colder Koue Bokkeveld and the warmer Grabouw regions.

    EXPERTISE: Dormancy Workgroup

    Research Team

    • Dr Esmé Louw
    • Dr Xolani Siboza
    • Dr Nigel Cook
    • Ms Laura Allderman
    • Dr Tara Southey
    • Dr Iwan Labuschagne
    • Mr Tristan Dorfling
    • Mr Chad van Wyk
    • Mr Andrew van Lingen – MSc student
    • Ms Anika Kock – MSc student
    • Mr Dian Craven – MSc student

    Projects list

    • Climate profiling and change analysis of the Elgin-Grabouw-Vyeboom- Villiersdorp (EGVV), Koue Bokkeveld (KBV) and Langkloof (LK) production areas specific to Pome fruit (T Southey) – See Growing season climate
    • Historic and future modelling and mapping of early season temperature patterns and extremes, and impacts for pome and stone fruit production in South Africa (S Midgley) - See Growing season climate
    • Adaptability indexing of new pome (apple and pear) and stone fruit (plum and cherry) cultivars in diverse South African growing areas (I Labuschagne, E Louw, A Kock and T Dorfling) – see Growing season climate [Abstract]
    • Investigating the significance of temperature on flowering phenology by establishing a South African apple and plum phenophase-temperature database (E Louw and I Labuschagne) [Abstract]
    • Rest breaking alternatives to hydrogen cyanamide. (C van Wyk) [Abstract]
    • Quantifying the impact of insufficient winter chill on apple fruit quality (E Louw and A van Lingen)
    • Leaf defoliation of Cripps' Pink and Granny Smith apples in the EGVV - effect on vegetative and reproductive development (X Siboza, K Theron and D Craven) – see Reproductive biology
    • Evaluation of alternative rest-breaking agents for apples (X Siboza, K Theron and D Craven) [Abstract]
    • Investigating the effect of different autumn/winter scenarios on the spring bud break in apple trees (E Louw and L Allderman) [Abstract]
    • Validation of the shoot assay as a proxy to determine the progression of dormancy in intact apple trees (E Louw and L Allderman) [Abstract]
    • Evaluate rest breaking programmes for warm winter regions. (X Siboza and D Craven) [Abstract]
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